Exercise Intolerance

I am 250 lbs. and have sleep apena. I cannot walk up 1 flight of stairs or 1 block without getting very short of breath , congested and then coughing for hours. this also happens if I get hot . I am active, as long as I dont over-exert or get hot.  I work every day and must walk alot during the day. But usually the unit is cool.    Because of this I cant exercise for anylength of time. I am too miserable  by the time I get started good. My doc. says there is nothing wrong with my lungs. Any suggestions for exercise that will help me build tolerance to activity ?

Do you have any type of exercise equipment at home or work out tapes?  I have a gazelle exercise gadget.  It gets me going.  Even if you can build up and do 10 minutes at a time 3/times a day it still equals 30 minutes of exercise. You may also want to try very simple strength training exercises instead of cardio aerobics.  Strength training with small hand weights can also build up your lungs if you follow proper breathing techniques.  You dont even have to buy weights, you can start out with smaller sized empty milk jugs filled with water or large canned goods.  Also is there anywhere near you with an indoor pool? Rosemary